JP3892822B2 - Information storage medium evaluation method and information storage medium evaluation apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an information storage medium such as an optical disk on which a wobble track is formed.The present invention relates to an information storage medium evaluation method and an information storage medium evaluation apparatus for evaluating the quality of an image.
[0002]
[Prior art]
As is well known, in recent years, as an optical disc capable of recording information at a high density, an optical disc having a single layer on one side and a capacity of 4.7 GB has been put into practical use. For example, there are a DVD-ROM which is a reproduction-only optical disc, a rewritable DVD + RW (ECMA-337), a DVD-RW (ECMA-338), and a DVD-RAM (ECMA-330).
[0003]
  An information recording layer is formed on the transparent substrate of these optical disks. This information recordlayerIs formed with a guide groove called a groove. Information is recorded on and reproduced from the optical disc along the guide groove. By condensing the laser beam on the guide groove of the information recording layer, information is recorded in the guide groove, or information recorded in the guide groove is reproduced.
[0004]
For example, a physical address for specifying a spatial position where information is recorded / reproduced is recorded in the DVD-RAM. For example, the physical address is formed so as to block the guide groove.
[0005]
On the other hand, in + RW, a physical address is reflected in the guide groove by using groove wobble modulation (hereinafter referred to as wobble modulation) that vibrates the guide groove in the radial direction. This is a method of changing the wobble phase in correspondence with information (physical address) to be recorded (Patent Document 1). The physical address recorded by such wobble modulation does not block the recording track. That is, the physical address recorded by wobble modulation does not press the user information recording area on the disc. For this reason, there are advantages such as excellent format efficiency and easy compatibility with a read-only medium.
[0006]
  As an evaluation index of the quality of the wobble signal obtained by optically reproducing the groove wobble, there is a narrow band signal to noise ratio (NBSNR) of the wobble signal. This evaluates the ratio between the amplitude of the carrier carrying the wobble signal and the amplitude of the noise. The higher the NBSNR, the higher the demodulation rate of the wobble signal. Also, this NBSNR is Carrier to NoiseRatioAlso called (CNR).
[0007]
[Patent Document 1]
JP-A-10-283737
[0008]
[Problems to be solved by the invention]
  Usually, the NBSNR of the wobble signal is measured from the difference between the peak value of the carrier frequency and the noise level around the carrier frequency by inputting the wobble signal to a frequency component analyzer such as a spectrum analyzer. However, when a modulation component is included in the wobble signal, the peak value of the carrier frequency is lower than the actual value. Further, the level around the carrier frequency is raised depending on the frequency of the modulation component. Therefore, modulation to wobble signalcomponentIf there is, there is a problem that the NBSNR of the wobble signal cannot be measured accurately.
[0009]
On the other hand, the wobble signal obtained from + RW includes two types of an unmodulated component and a modulated component, and most of them are unmodulated components. For this reason, it was possible to measure the NBSNR of the wobble signal with almost neglecting the modulation component. However, if the modulation area is reduced, the amount of information that can be recorded decreases. Therefore, this method cannot be used when the recording capacity of information by wobble modulation is increased.
[0010]
In order to maintain a high-quality wobble track, it is necessary to accurately measure the NBSNR of the wobble signal. If the NBSNR of the wobble signal cannot be measured accurately, there may be a problem that the quality of the wobble track is degraded. If the quality of the wobble track is poor, the physical address information reflected in the wobble track cannot be correctly reproduced, and as a result, there is a possibility that correct information cannot be reproduced from the disc. Similarly, there is a possibility that correct information cannot be recorded on the disc.
[0011]
  SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and is an information storage medium evaluation method capable of accurate performance evaluation.And providing an information storage medium evaluation apparatus.
[0012]
[Means for Solving the Problems]
  In order to solve the above problems and achieve the object, an information storage medium evaluation method of the present invention,And an information storage medium evaluation device,It is configured as follows.
[0013]
(1) The present invention provides an information storage medium comprising a wobble track that guides a light beam and is wobbled corresponding to a frequency whose phase is modulated at a predetermined timing in order to reflect predetermined information. An information storage medium evaluation method to be evaluated, wherein a reproduction signal corresponding to the wobble track obtained from reflected light of a light beam irradiated on the wobble track is doubled, and the frequency characteristic of the double reproduction signal is obtained. Based on this, the quality of the wobble truck is evaluated.
[0014]
(2) The present invention provides an information storage medium comprising a wobble track that guides a light beam and is wobbled corresponding to a frequency whose phase is modulated at a predetermined timing in order to reflect predetermined information. An information storage medium evaluation device for evaluation, the detection means for detecting reflected light of a light beam applied to the wobble track formed on the information storage medium, and the reflected light detected by the detection means Based on this, filtering means for removing noise from the reproduction signal corresponding to the wobble track, double multiplication means for multiplying the reproduction signal from which noise has been removed by the filtering means, and double reproduction that has been doubled by the double multiplication means Evaluation means for evaluating the quality of the wobble track based on the frequency characteristics of the signal.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present embodiment will be described with reference to the drawings.
[0020]
FIG. 1 is a block diagram showing a schematic configuration of an optical disc apparatus according to an embodiment of the present invention. The optical disk apparatus shown in FIG. 1 is an information reproducing apparatus and an information recording apparatus. That is, this optical disc apparatus records recording data on the optical disc D1 and reproduces recording data recorded on the optical disc D1.
[0021]
  As shown in FIG. 1, the optical disc apparatus is a controller.-10, a recording signal processing circuit 20, a laser driver (LDD) 30, a pickup head (PUH) 40, a photodetector (PD) 50, a preamplifier 60, a servo circuit 70, an RF signal processing circuit 80, an address signal processing unit 90, and the like. Yes.
[0022]
This optical disc apparatus records and reproduces information by condensing the laser beam emitted from the PUH 40 onto the information recording layer of the optical disc D1. The reflected light from the optical disc D1 passes through the optical system of the PUH 40 again and is detected as an electric signal by the PD 50.
[0023]
The PD 50 includes two or more light detection elements. A signal obtained by adding a plurality of electrical signals detected by each element is called a sum signal, and a signal obtained by subtracting a plurality of electrical signals detected by each element is called a difference signal. In particular, a sum signal to which high-frequency information such as user information is added is called an RF signal. A signal obtained by subtracting a signal obtained from each element optically arranged in the radial (radial) direction with respect to the optical disk is referred to as a radial push-pull signal.
[0024]
FIG. 2 is a diagram illustrating an example of a four-divided PD. As shown in FIG. 2, the PD 50 includes a quadrant photodetection element 51, adders 52, 53, 54, and a subtractor 55. Of the four signals detected by the light detection element 51, two signals are added by the adder 52, and the remaining two signals are also added by the adder 53. Further, the adder 54 adds the addition signal output from the adder 52 and the addition signal output from the adder 53 to generate a sum signal. That is, the sum signal is a signal obtained by adding all four signals detected by the light detection element 51. On the other hand, the subtractor 55 subtracts the addition signal output from the adder 53 from the addition signal output from the adder 52 to generate a difference signal. This difference signal is a radial push-pull signal.
[0025]
The electrical signal detected by the PD 50 is amplified by the preamplifier 60 and output to the servo circuit 70, the RF signal processing circuit 80, and the address signal processing unit 90.
[0026]
The servo circuit 70 generates servo signals such as focus, tracking, and tilt based on the electrical signal detected by the PD 50, and each servo signal is output to the focus, tracking, and tilt actuators of the PUH 40, respectively.
[0027]
The RF signal processing circuit 80 reproduces recorded user information and the like by mainly processing the sum signal among the electric signals detected by the PD 50. As a demodulation method at this time, there are a slice method and a PRML (Partial Response Maximum Likelihood) method.
[0028]
The address signal processing unit 90 reads the physical address information indicating the recording position on the optical disc by processing the electrical signal detected by the PD 50 and outputs it to the controller 10. Based on this address information, the controller 10 reads user information or the like at a desired position or records user information or the like at a desired position. At this time, the user information is modulated by the recording signal processing circuit 20 into a signal suitable for optical disc recording. For example, modulation laws such as (1, 10) RLL, (2, 10) RLL are applied. RLL is an abbreviation of run length restriction. (1, 10) RLL is a rule that limits the upper limit of the number of consecutive channel bits “0” to 10 and the lower limit of the number of consecutive bits to 1. That is, channel bits “0” continuously appear in the range of 1 to 10 on the disc recorded under the (1, 10) RLL condition. Similarly, channel bits “0” appear continuously in the range of 2 to 10 on the disc recorded under the (2, 10) RLL condition.
[0029]
An optical disc D1 according to an embodiment of the present invention includes a transparent substrate and an information recording layer laminated on the transparent substrate. As shown in FIG. 3, the optical disc D1 (information recording layer) includes an information recording area D12, and the information recording area D12 includes a guide groove (track D13) called a groove. The guide groove is called a track, and information recording / reproduction is performed along this track. As shown in FIG. 3, the track includes a spiral track D13 continuously connected from the inside to the outside of the disk and a concentric track formed of a plurality of concentric circles.
[0030]
FIG. 4 is a diagram showing an enlarged portion D13a of a part of the track D13 shown in FIG. As shown in FIG. 4, the track D13 is formed by the unevenness of the information recording layer. The concave portion is called a groove (groove track GT), and the convex portion is called a land (land track LT). The recording method includes a land groove method and a groove (land) only recording method. FIG. 4 is a diagram showing an example of a land groove system. As shown in FIG. 4, the land / groove method is a method for recording information (record mark RM) on both the land track LT and the groove track GT. On the other hand, the groove (land) only recording method is a method of recording information on only one of the tracks. The present invention can be applied to either method.
[0031]
FIG. 5 is a top view of a track formed on the optical disc. As shown in FIG. 5, the groove track GT and the land track LT are alternately formed. That is, the land track LT1 is formed between the groove tracks GT1 and GT2, and the groove track GT2 is formed between the land tracks LT1 and LT2.
[0032]
The tracks (groove track GT and land track LT) formed on the optical disk of the present invention meander slightly in the radial direction. Such a meandering track is called a wobble track D13. When the focused beam spot BS is scanned along the wobble track D13, the frequency of the wobble is higher than the bandwidth of the tracking servo signal, so the beam spot travels almost straight through the center of the wobble track. . At this time, as shown in FIG. 6, the sum signal hardly changes. On the other hand, as shown in FIG. 7, only the radial difference signal, that is, the radial push-pull signal changes in accordance with the wobble. This is called a wobble signal. The wobble signal is used for adjusting the rotation frequency of the spindle, recording clock reference, recording physical address information, and the like.
[0033]
  The optical disk of the present invention is formed with a wobble track wobbled corresponding to a frequency whose phase is modulated at a predetermined timing in order to reflect management information such as physical address information. That is, management information such as physical address information can be reproduced from a wobble signal obtained corresponding to a wobble track formed on an optical disc. For example, a wobble track wobbled corresponding to the phase-modulated frequency as shown in FIGS. 8 and 9 is formed. FIG. 8 is a diagram showing an example in which the phase-modulated frequency is reflected over the entire track. FIG. 9 is a diagram showing an example in which the phase-modulated frequency is reflected in a part of the track, and the non-phase-modulated frequency is reflected in the other part. In either case, the addresssignalThe processing unit 90 can read management information such as physical address information reflected on the track. addresssignalThe processing unit 90 includes a band pass filter 91, a wobble PLL 92, a symbol clock generator 93, a phase comparator 94, a low pass filter 95, a binarizer 96, and an address information processing circuit 97, as shown in FIG. . addresssignalThe processing unit 90 reads management information such as physical address information reflected on the wobble track from the radial push-pull signal supplied from the PD 50.
[0034]
FIG. 11 is a diagram illustrating frequency characteristics of a single frequency wobble signal that is not modulated. The frequency characteristic is the carrier frequency of the wobble signal (f₁) Has a peak, and other parts are noise components. As shown in FIG. 11, the NBSNR (or CNR) can be measured by determining the difference between the peak value and the noise level.
[0035]
FIG. 12 is a diagram illustrating the frequency characteristics of a binary phase modulation wobble signal having a phase difference between codes of about 180 degrees. The frequency characteristic is the carrier frequency (f₂) It rises in the vicinity, but peaks occur on both sides of the carrier frequency due to the influence of the modulation component, and its peripheral part also rises. Therefore, the NBSNR of the wobble signal cannot be obtained as shown in FIG.
[0036]
FIG. 13 is a diagram illustrating frequency characteristics of a wobble signal in which a modulation area and a non-modulation area exist at a ratio of 1: 4. Since the non-modulation region is long, the frequency characteristic is the carrier frequency (f₃), But the peak value decreases due to the influence of the modulation component, and the peripheral portion also rises. Accordingly, in this case as well, the exact NBSNR of the wobble signal cannot be measured as in the case of FIG.
[0037]
  In the present invention, the above-mentionedlikeIn order to accurately measure the NBSNR of the wobble signal, a double multiplied NBSNR is defined. This double NBSNR is the difference between the peak value appearing at twice the wobble carrier frequency and the noise level from the frequency characteristic resulting from double the wobble signal.
[0038]
  FIG. 14 is a diagram illustrating frequency characteristics of a doubled wobble signal obtained by multiplying a single frequency wobble signal that has not been modulated by two. FIG. 15 is a diagram illustrating frequency characteristics of a double wobble signal obtained by multiplying a binary phase modulation wobble signal having a phase difference between codes of approximately 180 degrees by two. FIG. 16 is a diagram illustrating frequency characteristics of a doubled wobble signal obtained by multiplying a partially modulated wobble signal by two. 14, 15, and 16, the doubled wobble signal is 2 × f₁2 × f₂2 × f₃It can be seen that the frequency characteristic is simple with only one peak. This is because only the carrier component of the wobble signal is extracted by multiplying the wobble signal by two. Therefore, if the difference between the peak value appearing at twice the carrier frequency and the noise level in the frequency characteristic after the double is obtained as a double NBSNR and the double NBSNR is evaluated, the accurate performance of the wobble signal can be obtained. I can grasp. Further, since this double NBSNR is a value obtained by subtracting about 6 dB from the NBSNR of the wobble signal before the double, the NBSNR can be estimated by adding 6 dB to the measured double NBSNR.
[0039]
In addition, the double NBSNR can evaluate the performance of the wobble signal in more detail than using the normal NBSNR. Usually, in order to evaluate the performance of a modulated wobble signal, it is necessary to evaluate the phase difference between codes in addition to the NBSNR of the carrier described above. For example, when a wobble signal subjected to binary phase modulation with a phase difference between codes of about 180 degrees is demodulated, if the phase difference of the actual wobble signal is reduced to 180 degrees or less, the demodulation at the time of demodulation is performed. This is because the error rate increases.
[0040]
FIG. 17 is a diagram illustrating frequency characteristics of a doubled wobble signal obtained by multiplying a partially modulated wobble signal by 2 when the phase difference of the wobble signal is reduced to about 160 degrees. Here, if the phase difference is 180 degrees, the carrier frequency can be extracted from the modulation factor by double as shown in FIG. 15 or FIG. However, if the phase difference deviates from 180 degrees, the carrier frequency cannot be extracted completely. As a result, as shown in FIG. 17, the peak is slightly lowered, and a slight rise occurs around the peak. As a result, the double NBSNR measured decreases. Therefore, it is possible to estimate the shift amount of the phase difference between codes from the amount of decrease of the double NBSNR. Thus, the double NBSNR can simultaneously evaluate not only the decrease in the amplitude of the basic component but also the phase difference of the modulation component.
[0041]
  FIG. 18 measures the NBSNR of the wobble signal obtained corresponding to the wobble track wobbled corresponding to the phase-modulated frequency.Frequency characteristicIt is a block diagram which shows an example of a measurement part. As shown in FIG.Frequency characteristicThe measurement unit 100 includes a low noise removal / amplifier 101, a band pass filter 102, a multiplier circuit (double multiplier) 103, and a frequency characteristic measurement circuit (spectrum analyzer) 104. As shown in FIG.Frequency characteristicThe reproduction signal evaluation apparatus shown in FIG. 19 can be configured by combining the measurement unit 100 and the optical disc apparatus shown in FIG. For example, thisFrequency characteristicThe output from the preamplifier 60 shown in FIG. 1 is input to the low noise elimination / amplifier 101 of the measurement unit 100, and thisFrequency characteristicThe output from the frequency characteristic measuring circuit 104 of the measuring unit 100 is the controller shown in FIG.-10 as entered in thisFrequency characteristicBy connecting the measurement unit 100 to the optical disc apparatus, the reproduction signal evaluation apparatus shown in FIG. 19 can be configured.
[0042]
That is, the radial push-pull signal output from the preamplifier 60, that is, the wobble signal, is input to the low noise elimination / amplifier 101 of the reproduction signal evaluation apparatus. The low noise removal / amplifier 101 removes a direct current component included in the wobble signal, appropriately amplifies the wobble signal, and supplies the wobble signal to the bandpass filter 102. The bandpass filter 102 removes excess frequency components included in the supplied wobble signal and supplies the wobble signal to the multiplication circuit 103. The extra frequency component is a frequency component sufficiently separated from the carrier frequency. The multiplication circuit 103 multiplies (multiplies) the supplied wobble signal, for example, generates a doubled wobble signal, and supplies this doubled wobble signal to the frequency characteristic measurement circuit 104. The frequency characteristic measuring circuit 104 measures the double NBSNR.
[0043]
Further, this measuring unit has the following characteristics in order to measure an accurate double NBSNR. The first is the band of the low noise removal / amplifier 101 and the multiplication circuit 103. As shown in FIG. 20, the low noise removal / amplifier 101 and the multiplication circuit 103 have a band that is at least six times the carrier frequency of the wobble signal to be measured. Specifically, when the carrier frequency of the wobble signal is about 700 kHz, the frequency at which the amplitude (level) ratio of the input signal to the output signal in the low noise elimination / amplifier 101 and the multiplication circuit 103 decreases by 3 dB is about 4 MHz to 5 MHz. It is.
[0044]
The second is the residual level in the carrier component included in the doubled wobble signal. When an ideal sine wave is doubled, a predetermined frequency (f₁, F₂, F₃) Has a peak level twice the predetermined frequency (2 × f) in the signal after the multiplication by two.₁2 × f₂2 × f₃). That is, the peak level at the predetermined frequency obtained from the frequency characteristic of the wobble signal appears at a frequency twice the predetermined frequency in the frequency characteristic of the doubled wobble signal. However, in actuality, in the frequency characteristics after doubled, the peak level (corresponding to the residual level of the carrier frequency does not appear only in the frequency twice the carrier frequency due to the noise of the wobble signal and the residual DC component). Residual peak level) also appears. The peak level corresponding to the residual level of the carrier frequency of the signal after doubled becomes noise for the measurement of doubled NBSNR. For this reason, the frequency characteristic measurement circuit 104 needs to sufficiently reduce the residual carrier component. Therefore, as shown in FIG. 21, the frequency characteristic measurement circuit 104 generates a peak level that appears corresponding to the residual level of the carrier frequency of the doubled signal at a frequency twice the carrier frequency. To 30 dB or more. In other words, the circuit characteristics such as frequency characteristics and delay are adjusted so that the residual peak level is 30 dB or more lower than the original peak level that appears at twice the predetermined frequency. That is, the difference between the first peak and the second peak of the output signal when an ideal sine wave is input is 30 dB or more. Thereby, the double NBSNR can be accurately measured.
[0045]
The third is the amplitude reduction ratio after multiplication by two. Usually, when the sine wave is multiplied by 2, its amplitude is reduced to about half, so that the CNR apparently decreases by about 6 dB. However, if the circuit delay or the frequency characteristics are poor, the amount of decrease in amplitude after double is large. If the amount of decrease is large, it is difficult to accurately measure the double NBSNR. Therefore, the frequency characteristic measurement circuit 104 has a difference between NBSNR and double NBSNR of 7 dB or less when a single frequency wobble signal or an input signal obtained by adding a noise component to an ideal sine wave is input. Have been adjusted so that. That is, when an unmodulated sine wave of NBSNR 30 dB is input, the double NBSNR becomes 23 dB or more. By satisfying at least one of the three characteristics described above, it is possible to accurately measure the double NBSNR.
[0046]
FIG. 22 is a diagram illustrating the relationship between the measurement result of the double NBSNR and the demodulation error rate of the modulated wobble signal. The demodulation error rate of the wobble signal is measured by, for example, the address information processing unit shown in FIGS. 1 and 10, and the double NBSNR is measured by, for example, the measurement unit shown in FIG.
[0047]
When physical address information or the like is obtained from a wobble signal, the demodulation error rate of the wobble signal is generally 1.0 × 10^-3It will be necessary to: If there are many demodulation errors above this error rate, the address information cannot be read accurately. As a result, a serious problem occurs such that reading of user information becomes impossible or information is recorded in an incorrect recording destination (address). Conversely, the demodulation error rate is 1.0 × 10^-3If it is below, it is possible to specify the physical address almost accurately by correcting the error and confirming the continuity of the addresses before and after.
[0048]
Here, from FIG. 22, the demodulation error rate is 1.0 × 10.^-3In order to secure the above, it can be seen that the double NBSNR is required to be at least 17 dB. Further, at this time, it is understood that the NBSNR before the multiplication by about 2 needs to be about 23 dB to 24 dB. That is, if the double NBSNR of the frequency characteristic obtained from the wobble track of the information recording medium shown in FIG. 3 is 17 dB or more, this information recording medium can accurately specify the physical address.
[0049]
Further, it is considered that the measurement circuit error and the reading error occur about 1 dB in the measurement of the double NBSNR. For this reason, it is better to ensure a double NBSNR of 18 dB or more for measurement. That is, if the measurement result of the double NBSNR of the frequency characteristic obtained from the wobble track of the information recording medium shown in FIG. 3 is 18 dB or more, the actual double NBSNR is reliably ensured to be 17 dB or more even if a reading error occurs. Will be. Therefore, this information recording medium can specify the physical address accurately.
[0050]
In addition, when address information is reflected in the wobble signal, it is difficult to reflect the error correction code together with the address information, or one address alone without considering the continuity of the previous and subsequent addresses in order to increase the access speed. In some cases, it is necessary to determine whether the physical address is read correctly or not. In such a case, a demodulation error rate of 1.0 × 10^-5The following needs to be ensured. Judging from the relationship of FIG. 22, the demodulation error rate is 1.0 × 10.^-5In order to ensure the following, the double NBSNR needs to be 19 dB or more. That is, if the double NBSNR of the frequency characteristic obtained from the wobble track of the information recording medium shown in FIG. 3 is 19 dB or more, this information recording medium can accurately specify the physical address even when there is no error correction code. In addition, high-speed access to a desired address becomes possible.
[0051]
FIG. 23 is a block diagram illustrating an example of a mastering apparatus that is a part of a manufacturing apparatus that manufactures the information storage medium illustrated in FIG. 3. The optical disc of the present invention is manufactured by the steps of master production, stamper creation, molding, medium film formation, and bonding. In the master production process, a resist is applied to the flat master D0, the resist on the master is exposed by the mastering apparatus shown in FIG. 23, and the exposed resist is removed by development, whereby information recording on the final optical disk medium is performed. Create a master with the same irregularities as the layer. In the stamper creation process, the master is plated with Ni or the like to form a sufficiently thick metal plate, and the master is peeled to produce a stamper. At this time, the uneven shape formed on the stamper is reversed with respect to the uneven shape formed on the master. Next, in the molding process, a stamper is used as a template, and a resin such as polycarbonate is poured into the stamper to mold the substrate. At this time, the unevenness of the surface of the molded substrate is a transfer of the unevenness of the stamper, that is, substantially the same as the unevenness of the master. Next, a recording material is formed on the uneven portion by sputtering or the like, and another substrate for protecting the formed portion is bonded to complete the optical disc D1. That is, the wobble track D13 is recorded by the mastering device shown in FIG.
[0052]
  As shown in FIG. 23, the mastering device is a controller.-110, formatter-120, wobble control circuit 130, laser driver (LDD) 140,Optical system150, a photo detector (PD) 160, a servo circuit 170, and a spindle slider 180.
[0053]
  FIG. 24 is a flowchart showing an outline of mastering processing by the mastering apparatus. controller-110 controls the entire mastering process. Formatter-120 acquires physical address information (ST11). This formatter-Based on the signal output from 120 to LDD 140,Optical systemThe laser light quantity of 150 is controlled. Laser light isOptical system150 passes through the AO modulator and objective lens included in 150, and is irradiated to the master D0. The servo circuit 170 controls the focus of the irradiation light, tracking, disk rotation, and the like. The portion of the master D0 irradiated with the laser light is exposed to light, and this portion becomes a guide groove (groove track) or the like.
[0054]
  Also the formatter-120 outputs a signal to the wobble control circuit 130 based on physical address information or the like to be recorded on the optical disc. The wobble control circuit 130 can slightly move the spot of the beam irradiated on the master in the radial direction by controlling the AO modulator and the like in the optical system unit. That is, the wobble control circuit 130 controls the AO modulator and the like in the optical system unit so that the double NBSNR obtained from the wobble track formed on the disc is 17 dB or more (ST12). ST11 and ST12 are repeated until a wobble track is formed on the entire surface of the disk (ST13). The optical disc produced by the above mastering process becomes an information recording medium that can correctly read the physical address.
[0055]
Next, with reference to FIG. 25, the quality evaluation of the reproduction signal by the reproduction signal evaluation apparatus will be described. As described above, the reproduction signal evaluation apparatus is configured by combining the measurement unit shown in FIG. 18 and the optical disc apparatus shown in FIG. The PUH 40 irradiates the wobble track D13 of the optical disc D1 with a light beam (ST21). The PD 50 detects the reflected light from the wobble track D13 (ST22). A radial push-pull signal generated from the signal detected by the PD 50, that is, a wobble signal is input to the measurement unit shown in FIG. The multiplication circuit 103 of the measurement unit multiplies the wobble signal by 2 (ST23). Based on the frequency characteristic of the doubled wobble signal, the frequency characteristic measuring circuit 104 of the measurement unit determines whether or not the result of evaluating the doubled wobble signal satisfies a predetermined evaluation index (ST24). That is, it is determined whether or not the difference between the peak level obtained from the frequency characteristic of the doubled wobble signal and the noise level (doubled NBSNR) is 17 dB or more. If the predetermined evaluation index is satisfied, that is, if the double NBSNR is 17 dB or more (ST25, YES), it is determined that there is no problem in the quality of the wobble track (ST26). Therefore, the physical address can be correctly read from the wobble track of the optical disc. Conversely, if the predetermined evaluation index is not satisfied, that is, if the double NBSNR is less than 17 dB (ST25, NO), it is determined that there is a problem with the quality of the wobble track (ST27). Therefore, the physical address may not be correctly read from the wobble track of the optical disc.
[0056]
Next, with reference to FIG. 26, reproduction processing by the optical disc apparatus shown in FIG. 1 will be described. The optical disk that is the target of the reproduction process is a disk that has been generated through the above-described mastering process and has been determined that there is no problem in the quality of the wobble track by the reproduction signal quality evaluation process. The PUH 40 irradiates the wobble track D13 of the optical disc D1 with a light beam (ST31). The PD 50 detects the reflected light from the wobble track D13 (ST32). A radial push-pull signal generated from the signal detected by the PD 50, that is, a wobble signal is input to the address signal processing unit 90. On the other hand, a sum signal generated from the signal detected by the PD 50, that is, an RF signal is input to the RF signal processing circuit 80. The address signal processing unit 90 reproduces physical address information based on the wobble signal (ST33). The RF signal processing circuit 80 reproduces recorded data based on the RF signal. This optical disc is a disc that has been generated through the above-described mastering process and has been determined that there is no problem in the quality of the wobble track by the reproduction signal quality evaluation process. Therefore, since the correct address is read from the wobble track of this optical disc, the target information can be read correctly. ST31 to ST33 are repeated until the reproduction processing of the target data is completed (ST34).
[0057]
Next, a recording process performed by the optical disc apparatus shown in FIG. 1 will be described with reference to FIG. The optical disk that is the target of the recording process is a disk that has been generated through the above-described mastering process and has been determined that there is no problem in the quality of the wobble track by the reproduction signal quality evaluation process. The PUH 40 irradiates the wobble track D13 of the optical disc D1 with a light beam (ST41). The PD 50 detects the reflected light from the wobble track D13 (ST42). A radial push-pull signal generated from the signal detected by the PD 50, that is, a wobble signal is input to the address signal processing unit 90. The address signal processing unit 90 reproduces physical address information based on the wobble signal (ST43). A target recording position is grasped based on the reproduced physical address information, and recording data is recorded at the target recording position grasped by the PUH 40 (ST44). This optical disc is a disc that has been generated through the above-described mastering process and has been determined that there is no problem in the quality of the wobble track by the reproduction signal quality evaluation process. Therefore, since the correct address is read from the wobble track of this optical disc, the target recording data can be correctly recorded at the target position. ST41 to ST44 are repeated until the recording process of the target recording data is completed (ST45).
[0058]
Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. In addition, the embodiments may be appropriately combined as much as possible, and in that case, the combined effect can be obtained. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.
[0059]
【The invention's effect】
  According to this invention,An information storage medium evaluation method and an information storage medium evaluation apparatus capable of accurate performance evaluation can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an optical disc apparatus (information recording / reproducing apparatus) according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a quadrant PD.
FIG. 3 is a diagram showing tracks on an optical disc according to an embodiment of the present invention.
FIG. 4 is an enlarged view of a wobble track formed on an optical disc.
FIG. 5 is a top view of a wobble track formed on an optical disc.
FIG. 6 is a diagram illustrating an example of a sum signal output from a photodetector.
FIG. 7 is a diagram illustrating an example of a difference signal (radial push-pull signal) output from a photodetector.
FIG. 8 is a diagram showing an example in which the frequency of phase modulation is reflected on the entire track.
FIG. 9 is a diagram illustrating an example in which a phase modulation frequency is reflected on a part of a track.
10 is a diagram showing a schematic configuration of an address signal processing unit shown in FIG. 1;
FIG. 11 is a diagram illustrating frequency characteristics of an unmodulated single-frequency wobble signal.
FIG. 12 is a diagram illustrating frequency characteristics of a binary phase modulation wobble signal having a phase difference between codes of about 180 degrees.
FIG. 13 is a diagram illustrating frequency characteristics of a wobble signal in which a modulation area and a non-modulation area exist at a ratio of 1: 4.
FIG. 14 is a diagram showing frequency characteristics of a doubled wobble signal obtained by multiplying an unmodulated single-frequency wobble signal by two.
FIG. 15 is a diagram illustrating frequency characteristics of a double wobble signal obtained by multiplying a binary phase modulation wobble signal having a phase difference between codes of approximately 180 degrees by two.
FIG. 16 is a diagram illustrating frequency characteristics of a doubled wobble signal obtained by multiplying a partially modulated wobble signal by two.
FIG. 17 is a diagram illustrating frequency characteristics of a doubled wobble signal obtained by multiplying a partially modulated wobble signal by 2 when the phase difference of the wobble signal is reduced to about 160 degrees.
FIG. 18 is a block diagram illustrating an example of a measurement unit that measures the NBSNR of a wobble signal.
FIG. 19 is a block diagram illustrating an example of a reproduction signal evaluation apparatus.
FIG. 20 is a diagram illustrating a relationship between an input / output ratio of a wobble signal and a frequency in a multiplication circuit.
FIG. 21 is a diagram showing a relationship between a peak value of a carrier frequency of a wobble signal after doubled and a peak value generated at a frequency twice the carrier frequency.
FIG. 22 is a diagram illustrating a relationship between a measurement result of double NBSNR and a demodulation error rate of a modulated wobble signal.
FIG. 23 is a block diagram illustrating an example of a mastering apparatus.
FIG. 24 is a flowchart showing an outline of mastering processing by the mastering apparatus.
FIG. 25 is a flowchart showing reproduction signal quality evaluation processing by the reproduction signal evaluation apparatus;
FIG. 26 is a flowchart for describing playback processing by the optical disc apparatus.
FIG. 27 is a flowchart for describing recording processing by the optical disc apparatus.
[Explanation of symbols]
10 ... Controller-20 ... Recording signal processing circuit, 30 ... Laser driver (LDD), 40 ... Pickup head (PUH), 50 ... Photo detector (PD), 60 ... Preamplifier, 70 ... Servo circuit, 80 ... RF signal processing circuit, 90 ... Address Signal processor 91: Band pass filter, 92 ... Wobble PLL, 93 ... Symbol clock generator, 94 ... Phase comparator, 95 ... Low pass filter, 96 ... Binarizer, 97 ... Address information processing circuit, 101 ... Low Noise elimination / amplifier, 102 ... band pass filter, 103 ... multiplication circuit (double multiplication circuit), 104 ... frequency characteristic measurement circuit (spectrum analyzer), 110 ... controller-120 ... Formatter-, 130 ... wobble control circuit, 140 ... laser driver (LDD), 150 ...Optical system, 160 ... photo detector (PD), 170 ... servo circuit, 180 ... spindle slider

Claims (5)

Information storage medium evaluation method for evaluating an information storage medium having a wobble track that guides a light beam and is wobbled corresponding to a frequency whose phase is modulated at a predetermined timing to reflect predetermined information Because
The reproduction signal corresponding to the wobble track obtained from the reflected light of the light beam applied to the wobble track is doubled, and the quality of the wobble track is evaluated based on the frequency characteristics of the double reproduction signal. A characteristic information storage medium evaluation method.   2. The quality of the wobble track is determined to satisfy a predetermined standard when a difference between a peak level obtained from a frequency characteristic of the double reproduction signal and a noise level is 17 dB or more. Information storage medium evaluation method. Information storage medium evaluation apparatus for evaluating an information storage medium, which is a track for guiding a light beam and includes a wobble track wobbled corresponding to a frequency whose phase is modulated at a predetermined timing in order to reflect predetermined information Because
Detecting means for detecting reflected light of a light beam applied to the wobble track formed on the information storage medium;
Filtering means for removing noise from the reproduction signal corresponding to the wobble track based on the reflected light detected by the detection means;
A doubler that doubles the reproduction signal from which noise has been removed by the filtering unit;
Evaluation means for evaluating the quality of the wobble track based on the frequency characteristic of the double reproduction signal doubled by the double means;
An information storage medium evaluation apparatus comprising: By the doubling means, when doubled sine wave of a predetermined sine wave is doubled is outputted, a peak level at a given frequency obtained from the frequency characteristics of the sine wave in the frequency characteristic of the doubled sine wave Appearing at twice the predetermined frequency,
The evaluation means has a characteristic of lowering the residual peak level corresponding to the residual level in the carrier component obtained from the frequency characteristic of the doubled sine wave by 30 dB or more from the peak level appearing at a frequency twice the predetermined frequency. ,
The information storage medium evaluation apparatus according to claim 3. When a doubled sine wave obtained by multiplying a predetermined sine wave including a noise component by the doubler is output by the doubler, the peak level at a predetermined frequency obtained from the frequency characteristic of the sinewave is the doubled sinewave. Appearing at a frequency twice the predetermined frequency in the frequency characteristics of
The evaluation means includes a first difference value between the peak level obtained from the frequency characteristic of the sine wave and the noise level, and a second difference between the peak level obtained from the frequency characteristic of the doubled sine wave and the noise level. Having a characteristic of making the difference value from the value 7 dB or less,
The information storage medium evaluation apparatus according to claim 3.

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